What do you think it would be like if you two met? Would you want to have an emotional discussion or could you do a light meet and greet? I can see where she's coming from on the "keeping it separate" and it's good that he wants to respect the time you and your wife have. I feel fairly certain, however, that I, personally, would not be happy not meeting the primary partner of my SO. Like Ari said, when you haven't met it's this big unknown and it's scary and intimidating. When you meet you can stop imagining and just get to know them. Some people like the DADT/separate approach. I like have those connections.